a) Field of the Invention
The invention relates to a regulator for automatically controlling length adjustment of a drive cable or Bowden cable to drive a vehicle brake by means of a drive element such as a brake lever or handbrake lever.
b) Description of Related Art
In general drive links/cables incur the drawback of slightly differing in length at manufacture and thereby precise length adjustment must be undertaken, especially when used as brake drive means. Moreover the drive cables elongate during operation and for instance the play of the brakes per se requires that the drive cables are adjusted during service life.
Such a regulator already is known from the German patent document 37 41 530 A1. This document proposes automatic adjustment in the cable lengths of parking brakes in the form of a resetting device fitted with an elongated transmission member which can be adjusted by a traction cable for the purpose of brake actuation, a double-arm adjusting yoke being mounted to said transmission member and being fitted with cables each leading to a wheel brake. The lever arms of the regulator yoke are supported in mutually pivotable manner, being prevented by a blocking device from transmitting braking force in one of the pivoting directions. A stressing means is used to constantly pivot the lever arms of the adjusting yoke into the other direction. In particular there is a transmission link between the U-legs of which a double-arm support yoke is supported so as to be pivotable about a stationary pivot axis. The support yoke consists of two yoke members, mounted in a common plane and each forming one lever arm, that are pivotable about a pivot axis and project from a longitudinal side of the transmission member. A stressing member is used to pivot the yoke members to adjust for elongations of the cables. This member preferably consists of a compression spring resting by each spring end against one of the yoke members. A locking device blocks the yoke members from rotating, ie pivoting opposite the tensioning direction of the cables. This locking device comprises a blocking pawl which is supported in pivotable manner, and furthermore in radially displaceable manner, relative to the pivot axis, said pawl serving as a rest for a return spring biasing the pawl towards its blocking position. A blocking toothing present at a yoke member at a peripheral sector is associated with the blocking pawl. Accordingly the pawl operates in step-wise manner and it will enter a new tooth-gap in the ratchet only after a predetermined elongation of the cable and then mutually locks the yoke members in a new relative position. Therefore locking comes about because the pawl in its engaging position can rest on a stop surface on one or both sides of the yoke member and because the yoke member is prevented from clockwise rotation by the cable. The design of this known adjusting device is comparatively complex and furthermore it is bulky.
The German patent document 43 02 250 C2 furthermore describes a vehicle brake system fitted with a cable tensioning means for a parking brake cable comprising a locking device which, when in the locked state, can be actuated in such manner that it will initially keep the adjusting ratchet locked relative to the lever against the biasing force of an adjusting spring in order to allow in this manner connection of the cable to the adjusting ratchet.
A further adjusting system is known from the German patent document 195 46 931 A1. To achieve automatic length adjustment, the adjusting system comprises an essentially box-shaped seat having two spring-loaded detent segments, detent levers or the like which are pivotable about different axes and which each can be connected by a drive cable, in particular a Bowden cable. This seat furthermore houses a blocking element displaceable therein and which, upon actuation of the drive cable or Bowden cable can be moved from a position unlocking the detent segments into a position locking them. Even though this known adjusting system has been found practical, more compactness is desired. In this respect it must always be borne in mind that the space available for the adjusting system, for instance in the vicinity of the drive lever itself, or in that region of the vehicle wherein the drive cables branch out to the two rear-wheel brakes, is small.